Cell culture is a technique having many applications; however some cells, such as tenocytes, hepatocytes, osteoblasts, myoblasts and cardiomyocytes can be difficult and/or slow to culture and/or tend to display an unstable phenotype and dedifferentiate in culture. The use of cultured tenocytes would have application inter alia in the repair of damaged tendons and ligaments.
One common example of damage to a tendon is a tear in the rotator cuff tendon. This commonly results from overhead activity and shows high clinical presentation. Loss of rotator cuff tendon integrity results in impaired strength measurements, and reduced range of motion and function. Although the surgical repair of rotator cuff tendon tears achieve high levels of functional improvement and patient satisfaction, some tendon repairs, especially of large and retracted tears, fail to heal or subsequently re-tear after surgery. Revision surgery for failed rotator cuff repair has very little success compared to primary treatment.
The fundamental principle of tendon repair is to prevent apoptosis of tenocytes and to restore normal tenocytes within the damaged tendon, but this requires the development of phenotypically stable tenocytes cultivated in vitro. However large numbers of tenocytes are required for the regeneration of a tendon or ligament. Moreover, the tenocytes should be of a phenotype as close as possible to that of tenocytes found in the body. Ideally, the cultured tenocytes are autologous for the subject requiring the tendon repair.
Currently, there are no adequate methods for culturing tenocytes to a sufficient degree of uniformity that they can be used to repair tendon or ligament damage. Many of the procedures described in the literature involve the culturing of intact tendons or, at best minced tendons, in the presence of growth factors such as insulin-like growth factors I or II (IGF-I or IGF-II) (see, for example, Dahlgren et al., 2001, AJVR, 62(10): 1557-1562; Kang & Kang, 1999, Yonsei Med. J., 40(1): 26-29; Abrahamsson, 1996, J. Ortho. Res., 15: 256-262; Abrahamsson & Lohmander, 1996, J. Ortho. Res., 14: 370-376; Abrahamsson et al., 1991, Ortho. Res. Soc., 9: 495-502 & 503-515; and Anitua et al., 2005, J. Ortho, Res., 23: 281-286). While these methods demonstrate growth enhancement of “tendon-like” or “tendon-derived” cells it is well established that tendons do not solely comprise tenocytes. Indeed, most of the cells in tendons are fibroblasts along with endothelial cells, synovial cells and some chondrocytes. Accordingly, the known methods for culturing tendon cells do not result in pure cultures of tenocytes, but a mixed population of cells comprising fibroblasts, endothelial cells and a small number of tenocytes. It is well-known that tenocytes are slow growing cells and as such are often overgrown by other cells present in culture. This means that the prior art methods for culturing tendon-derived cells generally produce insufficient tenocytes for their use in tissue repair procedures.
Accordingly there is a need for a method for culturing tenocyte cells sufficient to enable their use in tissue repair procedures.